Armor-plate and other steel article.



F. GIOLITTI. ARMOR PLATE AND OTHER STEEL ART IOLE.

APPLIOATION FILED 0C1.10 1907.

Patented Feb. 6, 1912.

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UNITED STATES PATENT onrion.

FEDERIG O GIOLTTTI, OEROME, ITALY, ASSIGNOB, TO SOCIETA ANONIMA ITALIANOGIO ANSALDO ARMSTRONG 80 (30., OF GENOA, ITALY, A COMPAN T INCORPORATEDIN ITALY.

ARMOR-PLATE AND OTHER STEEL ARTICLE.

Specification of Letters Patent.

Patented Feb. 6, 1912.

Originaliapplication filed September 6, 1906, Serial No. 333,408.Divided and this application filed October To all whom it may concern Beit known that I, FEDERICO GIoLrrrI, a subject of the King of Italy,residing in Rome, Italy, have invented certain new and useful.Improvements in Armor-Plates and other Steel Articles, of which thefollowing is a specification.

This application is a division out of an application filed in the UnitedStates Patent Ofiice Sept. 6, 1906, Serial No. 333,408.

This invention relates to armor plates or other objects made of steel,composed of either superficial or deep successive zones in steels ofdifferent composition, not only as regards the proportion of carboncontained but also as regards the presence in some of them of foreignmetals and as regards the proportions in which these metals enter intothe composition. This latter varies gradually in passing from one zoneto another. The accompanying drawing illustrates diagrammatically asteel plate after treatment according to the present invention.

The result in question is obtained by submitting the mass of homogeneoussteel (either ordinary carbon steel or a special ternary, quaternary orlike steel) to the action of suitable granular mixtures contain.- ingthe metal it is desired to introduce into the steel, such for instance,as chromium,

nickel, tungsten, molybdenum, manganese,

Vanadium and sometimes silicon and uranium in a free state or in a statereadily dis-' associated under certain conditions, which, as hereinafterset forth, varies from one preparation to the other as well as from onephase to the other of the same preparation. These granular mixtures arestrongly pressed against one or both surfaces of the plate or otherarticle that is treated.

For each given composition of the homogeneous steel which forms the massunder manipulation, as well as for one or more of the given metalscontained in the mixture employed, there exists a determined range oftemperature, which depends strictly on the range of the critical pointsof the homogeneous steel itself, and on the nature of the metalsemployed. It is in this range that occurs the diffusion of the metal ormetals contained in the mixture pressed against the surfaces of the massof steel, toward the interior of the mass. The range of temper- 10,1907. Serial No. 396,864.

comprised between the temperature of the first critical point of thesteel employed and a temperature below its point of fusion. The depth towhich the metal contained in the granular mixture-extends into thehomogeneous mass of steel submitted to such an operation, dependsprimarily on the duration of the operation; but even by considerablyprolonging this duration, a very deep or gradual diffusion would not beobtained in the'greater number of cases if the temper ature were alwaysmaintained constant from thebeginning of the operation until the end.

The constancy 6f the temperature-a condition which would be very usefulif a certain concentration as regards the, foreign metal introduced hadnot been surpassed,

and if a great homogeneousness of cOncentration for a given zone of theplate had to be obtained, prevents a very definite given limit ofconcentration being surpassed, because if this latter is increased thereis produced a displacement of the critical points and consequently ofthe interval of temperature in which the diffusion can be effected. Itresults that at a certain moment the temperature maintained constant isno longer comprised in this interval and consequently the passage of themetal of the mixture to the mass under treatment is no longer effectedand the difi'usionis effected only at the interior of the mass until theconcentration is suitably lowered owing to the interior diffusionreferred to. It will then generally be advisable to suitably alternatethe reduction and the increases of temperature in limits which caneasily be determined for each. case and which generally ought todetermine the critical points.

The product of the treatment referred to above will consist of aheterogeneous mass of steel, the composition of which varies in thevarious zones or layers according to the composition of themicro-construction of the homogeneous steel at the beginning, the

composition of the granular mixture em have (as well as the ternaryzone) the same end. As example a steel carbon plate initial proportionof carbon, or a different proportion according as the granular mass didor did not containactive substances or was more or less rich in carbonor metazllic 0.1 to 0.2 per cent. of'carbon) may be taken, maintained incont-act with a mixture of wolframic acid and of substances suitablycarbonaceous, or nitrogenous, compressed against one of its surfaces ata temperature near that of fusion. As an example of such steel andWolfram nitrogenous substances may be mentioned: charcoal 50% barium25%, and ferrocyanid of potassium 5%. In this case the precedingoperation must be followed by a'superficial de-carbonization, obtainedby means of heating in contact with mixtures of metallic oxids. On thecontrary, ifa start is made with a ternary homogeneous steel ingot (forexample, a chrome steel with two to four per cent. of chromium) thefinal product will have a structure similar to that of the former ingot,but the layer of ternary steel would be substituted by a layer ofquaternary steel, while the rest of the body would still be ternarysteel. In the case just mentioned, by employing a mixture of thepreceding case, the quaternary layer will consist of chrome steel. Theprocedure is followed in a similar manner for the more complex steels.

Similar considerations will apply in the case where the treatment bydiffusion is effected on two surfaces or on all the surface of the steelobjects, in one, two, or more times; these operations alternating withthermic treatment (temperings and the like) or suitable mechanicaloperations which may vary for each case according to the nature of thesteel employed and of the steel desired to be obtained. The operationjust referred to may be applied directly to the mass of homogeneoussteel as cast, or to the mass when brought to the desired shape by themechanical manipulations, such as hammering, rolling, pressing and thelike. In every instance, however, it would almost always be necessary tofollow the chemical treatment described by a suitable thermic treatment.But it is in the temper of the metallic bodies where the greatestadvantages of this method of manufacture and the superiority of thebodies produced in this manner,

elasticity and bone black 20%, carbonate of are evident as compared Withthose obtained by other methods. As a matter of fact, by employing thismethod, any desired composition for the various zones of the body ofsteel, can be obtained, and consequently various parts of the object maybe given the most suitable composition by means of a homogeneoustempering applied to the whole whereby each part acquires physical,chemical or mechanical properties (such as magnetic properties,resistance to chemical agents, hardness, plasticity, the like) the mostsuit able for the purposes for which the bodies are to be employed. Bythis method, armor plates for example, can be obtained which, after oneor more omogeneous temperings efl'ected under the desired conditions oftemperature and the like, possess mechanical properties (hardness,tenacity, and the like differing in the various layers so that they canbe most suitably adapted to the mostvaried uses.

Let us suppose for example to have to do with a special nickel steelshowing'the following composition: Nickel 2.20%, carbon 0.10%, manganese0.42%, silicon 0.30%, sulfur 0.04% phosphorus 0.02%, and that it beintended to obtain a zone of 3 mm. thickness, in which the percentage ofcarbon should vary from 0.9% (on the outer face) down to 0.4% at 3 mm.depth, while the percentage of manganese, namely of the metal to beintroduced by diffusion according to the present invention should varybetween 3% (on the outer face) and 0.7% at 3 mm. depth. In order toobtain this result it will be suflicient to heat the steel piece incontact with a granular mixture consisting of three parts of charcoal,one of finely pulverized manganese dioxid and one of barium carbonate. Atemperature of 1150 degrees C. is to be kept up during about half anhour; whereupon the same is to be allowed to gradually drop down to 700degrees C. at the end of three hours. In making these statements, as tothe duration of the heating, it has been assumed that the time begins torun since the full heat has been laid on the steel pieces; theadditional time necessary for reaching the aforesaid temperatures aswell for cooling after each treatment, of course depends upon the sizeof the pieces and the arrangement of the heating furnaces.

Having described my invent-ion I claim:

1. A steel plate or other article having on one or more surfaces a zoneof considerable thickness throughout which is diffused a characteristicmetallic steel component not contained in the other part of the article,the said metallic component being graded from a maximum inwardly to aminimum, such zone having a less p'ro ortion of carbon than in the otherportion of the article.

2. A ternary steel plate or other article less proportion of carbon thanin the other having on one or more surfaces a quaternary portion of thearticle. 10 zone of considerable thickness throughout Signed at Nos.9-15 Murray street, New which is diffused a characteristic metallicYork, N. Y., this first day of October, 1907.

5 steel component not contained in the other FEDERICO GIOLITTI.

part of the article, the said metallic com- Witnesses: ponent beinggraded from a maximum in- WILLIAM H. REID,

wardly to a minimum, such zone having a FRED. J (DOLE.-

